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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Bradycardia is strictly defined in adults as a pulse rate below 60 beats per minute (bpm). However, few individuals are symptomatic unless the heart rate is below 50 bpm. Top endurance athletes may have a resting heart rate in the very low 30s without needing any intervention with anticholinergics, isoprenaline, adrenaline (epinephrine), chest compressions or the insertion of an emergency pacemaker.[1]

Physiologically, heart rate can vary in normal adults from 40 bpm up to 180 bpm. However, a relative bradycardia may be greater than 60 bpm if that rate is too slow for the haemodynamic requirements of the patient.

Children tend to have a higher resting pulse rate than adults and generally the smaller they are, the faster the heart rate. Hence, in a neonate, bradycardia may be defined as a rate below 100 bpm.

Epidemiology

It is impossible to give meaningful figures on incidence and prevalence. In most young people bradycardia is physiological and represents athletic training. The incidence of pathological bradycardia rises with age as the underlying causes become more frequent.

Presentation

Bradycardia may be asymptomatic but can present with syncope, fatigue or dizziness. Ischaemic chest pain, Stokes-Adams attacks, hypoxic seizures, congestive heart failure, cardiovascular collapse and sudden cardiac death may occur, depending on the underlying cause of bradycardia.[2]

History

Establish whether there is any history of chest pain or collapse.

Ask whether there is any shortness of breath on exertion. It is important to ask about exercise and tolerance of exercise. An athlete with a resting bradycardia will raise heart rate and cardiac output to meet demand. Anyone who can sustain even moderate exercise without undue distress is most unlikely to have a pathological cause.

Ask whether the patient is aware of heart rate - whether it is always slow or just at times; whether there are any 'thumps' in the chest, extra or missed beats.

Establish whether there is a history of faintness, dizziness, nausea or chronic fatigue.

It is important to ask about medication, as drugs are an important cause of bradycardia.

Examination

Note whether the patient looks well or there are signs of inadequate cardiac output - for example, cold peripheries, peripheral cyanosis or features of congestive cardiac failure.

Examination of jugular venous pressure (JVP) may reveal:

Elevation of the JVP in heart failure.

Cannon waves, which may be seen in complete atrioventricular (AV) dissociation. This is an intermittent very high jugular pulse as the atrium contracts against a closed tricuspid valve.

Examine the pulse carefully and count for at least 30 seconds (the slower the rate, the longer the duration). An athlete may show sinus arrhythmia but this is rare beyond 30.

Note any shift in the cardiac apex.

Aetiology

Sinus bradycardia may be physiological with a high resting vagal tone - eg, in athletes or the diving reflex.

If response is not satisfactory, repeat atropine up to a maximum total dose of 3 mg OR transcutaneous pacing OR consider alternative drugs, such as isoprenaline infusion or adrenaline (epinephrine) infusion.

Further alternatives include:

Aminophylline

Dopamine: 5-20 micrograms/kg/minute through central line.

Glucagon (if bradycardia is caused by a beta-blocker or a calcium-channel blocker).

Glycopyrrolate (may be used instead of atropine).

Once there is a satisfactory response, continue observation if there is a risk of asystole (recent asystole, Mobitz II AV block, complete heart block with broad QRS, ventricular pause >3 seconds).

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

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